The present invention relates to solvent resistant vulcanizable silicone rubber compositions, and more particularly, the present invention relates to an improved one- or two-component room temperature vulcanizable silicone rubber composition having vinyl-chain stopped units and fluorinated substituent groups. The polymers are cured in the presence of a catalyst with a hydrosiloxy polymer cross-linking agent having fluorinated substituent groups in the polymer, to form solvent resistant elastomers.
Silicone elastomers are well known in the art and are used for many applications in which high and low temperature stability are desired.
One class of solvent resistant room temperature vulcanizable silicone rubbers is disclosed in U.S. Pat. No. 4,041,010 which is incorporated herein by reference. The solvent resistant room temperature vulcanizable silicone rubber compositions disclosed and claimed in U.S. Pat. No. 4,041,010 comprise (A) 100 parts of a mixture composed of (i) 100 parts of a vinyl-containing polymer of the formula, ##STR1## where Vi is vinyl, R is selected from the class consisting of alkyl radicals of 1 to 8 carbon atoms and phenyl, R' is perfluoroalkyl of 1 to 8 carbon atoms, x and y are at least 1, and the viscosity of the compound varies from 1,000 to 500,000 centipoise at 25.degree. C., and the concentration of the siloxy units taken y times varies from 5 to 98 mole percent; (ii) from 1 to 60 parts of a vinyl-containing resin selected from the class consisting of a resin having ViRR"SiO.sub.0.5 units and SiO.sub.2 units where the hydrocarbon substituent to Si ratio varies from 0.8 to 2.7; a resin having ViRR"SiO.sub.0.5 units, SiO.sub.2 units and RR"SiO units where the hydrocarbon substituent to Si ratio varies from 0.8 to 2.4; a resin having ViR.sub.2 SiO.sub.0.5 units, R.sub.2 R"SiO.sub.0.5 units, SiO.sub.2 units and RR"SiO units where the hydrocarbon substituent to Si ratio varies from 0.8 to 2.4; and a resin having R.sub.2 R"SiO.sub.0.5 units, SiO.sub.2 units and ViR"SiO units where the hydrocarbon substituent to Si ratio varies from 0.8 to 2.4, where Vi and R are as previously defined, R" is selected from the class consisting of alkyl radicals of 1 to 8 carbon atoms, phenyl radicals and --CH.sub.2 CH.sub.2 R' radicals, where R' is as previously defined; (iii) from 0.1 to 50 parts per million of the total composition of a platinum catalyst; and (B) from 1 to 50 parts based on 100 parts of the mixture of (A) of a cross-linking polymer selected from the class consisting of (iv) a resin having ##STR2## units and SiO.sub.2 units where the R+R'"+H to Si ratio varies from 1.0 to 2.7; (v) a resin having ##STR3## units, SiO.sub.2 units and RR'"SiO units where the R+R'"+H to Si ratio varies from 1.2 to 2.7 and (vi) a polymer of the formula and mixtures thereof and where the concentration of the units taken t times varies from 0 to 75 mole percent; where R and R' are as previously defined, s is at least 1, t and z may be zero or a positive integer, and the viscosity of the polymer varies from 10 to 1000 centipoise at 25.degree. C., and R'" is selected from the class consisting of alkyl radicals of 1 to 8 carbon atoms and --CH.sub.2 CH.sub.2 R' radicals.
Another class of solvent resistant room temperature vulcanizable silicone rubbers is disclosed in U.S. Pat. No. 4,029,629 which is incorporated herein by reference. The solvent resistant room temperature vulcanizabale silicone rubber compositions disclosed and claimed in U.S. Pat. No. 4,029,629 comprise: (A) 100 parts of a mixture composed of (i) 100 parts of a vinyl-containing polymer of the same formula designated as formula (1) above, where Vi, R, R', x and y are the same as defined for formula (1) above and the viscosity and the concentration of siloxy units taken y times is the same as defined for formula (1) above; (ii) from 0.1 to 50 parts per million of the total composition of a platinum catalyst; and (B) from 1 to 50 parts based on 100 parts of the mixture of (A) of a cross-linking polymer selected from the class consisting of (iii) a resin having ##STR4## units and SiO.sub.2 units where the R+H+R" to Si ratio varies from 1.0 to 2.7; (iv) a resin having ##STR5## units, SiO.sub.2 units and RR"SiO units where the R+H+R" to Si ratio varies from 1.2 to 2.7; and (v) a polymer having the same formula designated as formula (4) above and mixtures thereof where the concentration of the units taken t times varies from 0 to 75 mole percent, where R and R' are as previously defined, s is at least 1, t and z may be 0 or a positive integer, and the viscosity of the polymer varies from 10 to 1000 centipoise at 25.degree. C., and R" is selected from the class consisting of alkyl radicals of 1 to 8 carbon atoms and --CH.sub.2 CH.sub.2 R' radicals. In U.S. Pat. No. 4,029,629, the vinyl-containing polymer of formula (1) may optionally contain from 1 to 85 parts per 100 parts of polymer (i) of a vinyl-containing compound of the formula: ##STR6## where R, Vi and R' are as previously defined; v and w are at least 1, and the concentration of the Vi(R).sub.2 SiO.sub.0.5 units with respect to the total terminal units in the polymer varies from 20 to 100 mole percent, and the viscosity of the polymer ranges from 100 to 20,000 centipoise at 25.degree. C. In formula (6), v and w are positive integers of at least 1, and generally v varies from 1 to 800, and w varies from 1 to 800 such that the final viscosity of the polymer at 25.degree. C. can vary from about 1,000 to about 2,000,000 centipoise and preferably from about 1,000 to about 500,000 at 25.degree. C.
The foregoing compositions described and claimed in U.S. Pat. No. 4,041,010 and U.S. Pat. No. 4,029,629 overcome many prior art deficiencies by having superior solvent resistance to hydrocarbon fluids, good physical properties and a fast cure rate at elevated temperatures even though the compositions are SiH-olefin platinum catalyzed silicone rubber compositions having fluorinated substituent radicals.
Although the elastomers of U.S. Pat. Nos. 4,041,010 and 4,029,629 have good elastomer properties, it is desirable to improve the properties of the elastomers for various uses. For example, it is desirable in most instances to improve the miscibility of the fluid/resin blends and to obtain clear solutions which show no tendency to separate into layers upon standing. It is also desirable to obtain cured elastomers which are clear. Furthermore, it is desirable to overcome the deficiency found in many of the prior art fluid/resin blends and cured elastomers (a) in which cloudy mixtures are obtained; (b) in which the components separate upon standing; and (c) wherein the elastomers appear somewhat cloudy or hazy.